luogu 2219[HAOI2007]修筑绿化带 单调队列

Code:

#include<bits/stdc++.h>
using namespace std;
#define setIO(s) freopen(s".in","r",stdin)
#define maxn 1002
#define inf 1000000000
deque<int>q;
int n,m,A,B,C,D;
int minv[maxn][maxn],sumv[maxn][maxn],val[maxn][maxn],tot[maxn][maxn];
int main()
{
    // setIO("input");
    scanf("%d%d%d%d%d%d",&n,&m,&A,&B,&C,&D);
    for(int i=1;i<=n;++i)
    {
        for(int j=1;j<=m;++j)
        {
            scanf("%d",&sumv[i][j]);
            sumv[i][j]+=(sumv[i][j-1]+sumv[i-1][j]-sumv[i-1][j-1]);
        }
    }
    for(int i=1;i<=n;++i)
    {
        for(int j=1;j<=m;++j)
        {
            if(i>=A&&j>=B) tot[i][j]=sumv[i][j]-sumv[i-A][j]-sumv[i][j-B]+sumv[i-A][j-B];
            if(i>=C&&j>=D) val[i][j]=sumv[i][j]-sumv[i-C][j]-sumv[i][j-D]+sumv[i-C][j-D];
        }
    }
    for(int j=1;j<=m;++j)
    {
        while(!q.empty()) q.pop_front();
        for(int i=2;i<=n;++i)
        {
            while(!q.empty()&&i-q.front()+1>=A-C) q.pop_front();
            if(!val[i-1][j]) { minv[i][j]=inf; continue; }
            while(!q.empty()&&val[i-1][j]<=val[q.back()][j]) q.pop_back();
            q.push_back(i-1);
            minv[i][j]=val[q.front()][j];
        }
    }
    int ans=0;
    for(int i=1;i<=n;++i)
    {
        while(!q.empty()) q.pop_front();
        for(int j=2;j<=m;++j)
        {
            while(!q.empty()&&j-q.front()+1>=B-D) q.pop_front();
            if(!val[i][j-1]) continue;
            while(!q.empty()&&minv[i][j-1]<=minv[i][q.back()]) q.pop_back();
            q.push_back(j-1);
            ans=max(ans, tot[i][j]-minv[i][q.front()]);
        }
    }
    printf("%d\n",ans);
    return 0;
}